Fluid tachometer



I 1,613,727 11 1927' H. F. SCHMIDT FLUID TACHOMETER FiledDec. 17, 1924 INVENTOR ATTORNEY Patented Jan. 11, 1927.

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- FLUID TACEOKETER.

Application filed DI'ecemhpHY, 1924. Serial-No. 750.424.

My invention relates to tachometers, parslightly varying speeds "when under load the 50 ticularly to tachometers which are actuated vibration of the machine is not enough to by fluid pressure, and it has for an object set the reeds vibrating with sufiicient amto provide apparatus of the character des plitude' to insure a positive indication of-the ignated which shall indicate accurately the speed at any instant. angular. velocity of a rotating body and I have therefore developed a form of tawhich shall have embodied within the tachometer which is especially adapted for use chometer means for readily determining the with high s eedrotary machines, as steam accuracy" of the, velocity indicated. turbines, which are frequently provided with 'These and other objects, which will be fluid pressure generat ng me s, the fluid made apparent throughoutthe further depressure generated being utilized to govern 60 I scription of my invention, may be attained the speed'of the turbine or to convey lubriby the employment of the apparatus hereincant to the bearings; The pressure develop after described and illustrated in the accoming apparatus generally employed comprises panying drawing, in which Fig. 1 is a diaa pump of the lmpeller type which is driven grammatie arrangement of a prime mover by the shaft of the turbine, the pressure equipped with one formof y tlachometer developed by the pump varying as the. uare for indicating its rotational velocity; Fig.- 0f the R. P. M.- of the shaft- I hav 2 is a View, in elevation, of the tachometer fore-devised a ytllchometer which is actuated employed in Fig. 1; Fig. 3-is a View, in see by fluid pressu -It comprises a Bourdon tional elevation, of th'e tachometer and Fig. tube having suitable mdicatin means asso- 7 4 is a partial sectionaluiew tak n on, the c'iated therewith, which indicatlng means are line IV IV of Fig, 2, graduated preferably in R. Pa; M. For

Machines of th high speed rota ry type, checklng the accuracy of'the device at all such as steam turbines, centrifugal) um 's, times, I have associated therewith a vib'r'at-" blowers, etc., are generally provide "w th 1119, element,- IG as a feed. Which flP suitable devices for indicating their rotad to Vibrate at a pl edetermmedspeedl tional velocities. One 'form of indicating noting, the posltion of the indicator at this device which is frequently associated with speed,- the indications of the tachometer steam turbines isa tachometer of the vibratmay be easily verlfied and, if, fpund inac' ing reed type. In this .type of indicating curate, the necessary ad'justments'may be 39 device, a. pluralitypf ibrating elements or eii'ected. I prefer to provide a reed having reeds having relatively difl'erent periods of adiiierent period of vibration from that vibration are employed, and the number of incident to the normal operating speed of revolutions per minute, is ascertained by notthe machine, the reed remainlng normaliy ing the reed or reeds which aredin vibration. inactive. Upon starting the machine, how- 3% However, as it is generally customary to-opiever", and beforeg-it has acquired its normal erateturbines at a substantially constant qoperating'speed, the rotations of the machine speed, the reeds corresponding to that speed, may be made such as to utilize the reed to as a result of'continuous vibration, become test the accuracy of the tachometer.

fatigued and eventually fail. Furthermore, owing to the highly developed state to which 1 l a rotary machlne, such as .aturbine .10,\ the static and dynamic balancing arts have provided with ashaft ll supported in suit-' recently been developed, rotary F'machines able bearings 12 and '13. Qonnected tothe may now be so accurately balanced that the shaft 11 is a pump 14 havmg an inlet con vibrationincident to their designe -operatnection 15 and a-discharge connection 16. ing speeds is almost nil. Under these coli- The pump discharges through a conduit 17 ciitions, tachometers of the vibrating reed which commumcateswith one form of my type maybe rendered ineffective, as with novel tachometer The conduit 1?" fur- Re'ferring. to the drawing, I show in Fig.

ther communicates through a conduit -19 with a pressure. responsive mechanism 21 which actuates, through a lever 22, a valve 23 for controlling the admission'of motive fluid to the turbine. The pressure-responsive mechanism 21 regulates themovements of the valve 23 in accordance with the pres I resistance to flow encountered by the lubricant in its passage through the bearings. The lubricant drainage from the bearings is conveyed by conduits 27 and 28 to a reservoir 29. The suction connection. 15 of the pump 14 communicates, through a conduit 31, with the reservoir 29 for re-circulating the lubricant through the system.

The tachometer 18 comprises, as shown in Figs. 2

therein a fluid pressure inlet 36. Connected to the inlet 36 is a Bourdon tube 37, or anysuitable pressure-responsive element, which in *turn is operatively connected through a link 38 and gears 39 and 41 to a shaft 42.-

Secured to the shaft 42 is a pointerv 4 3, the movements of which are controlled by the pressure generatedby the pump 14. J Some suitable means such as-a spring'44 is pro;

vided for biasing the shaft and pointer to a 7 zero position. The tachometer is provided with a dial 45 which is preferably graduated, as illustrated, in R. P. M The/dial is adjustably secured to the casing 35 as by suitable screws 46 located in arcuate openings 47 by means of relative to the pointer and the indications of be found inaccurate.

the tachometer easily corrected, should they curacy of he device 'may at all times be readily determined, 1 have provided areed 48 which is visible through a suitable aperture 49 provided in the dial. The reed 47 has a period of vibration corresponding to that of the turbine at the speed at which it is desired to test the accuracy of the device.

From theforegoing description of my apparatus, it will be apparent that I have devised a novel form of tachometer which is sensitive to changes in rotationalvelocity and which is furthermore provided with a novel means for checking the accuracy of the speed indicated. While I have described my device as being provided with only a'single vibrating element, it. is to be understood that it is .within' the purview of my invention to-employ a plurality of reeds for ascertaining 14 also communicates claims.

and 3, a casing 35 having-provided which the dial .may be rotated In order that the ac-' 5. The combination with a-rotating the accuracy of the tachometer at an desired number of points. In addition, while I have illustrated my invention as being associated with steam turbines, its use is not confined solely thereto. and it may be readily em ployed with numerous forms of rotatable machinery having means for developing a fluid pressure proportional to their rotational velocity.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed there upon as are imposed by the PIlOl art, or as are specifically set. fonth in the appended WhatIclaim is:

1, The combination with a pressure-re:

sponsive mechanism for indicatin the speed of a moving body having means f dr generating a fluid pressure which is a function of 1 its speed, of an element vibrated by the moving body at a predetermined speed for testing the accurac of the indicating mecha nism, said pre etermined speedidifiering from the normal speed of the moving body.

2. The combination with a fluid tachometer for indicating the speed of a rotating body having means for generating a fluid pressure which is a function of its rotational velocity, of a vibrating element associated with said mechanism, said element being vibrated by the body at a predetermined speed for ascertainin the accuracy of the tachometer, said predetermined speed diflffging from the normal speed of the rotating o Y 3 The combination with a Bourdon tube responsive to fluid ressure generated by a rotating body as a unction of its rotational velocity, of a dial, means operatively connected to the Bourdon tube for indicating upon thedial the rotational speed of the body, a reed vibrated by the rotating body and having a predetermined period of vibration for ascertaining the accuracy of the Bourdon tube said period not corresponding with the norma speed ofthe rotating body, and adjustable means 'for positioning the dial with respect to the indicatin means.

\ 4. The combination with a Bour on tube of means associated with said body for gencrating a fluid ressure whieh is {fume-w fer ca librating the reesuieresponof its mtat-iona velocity, 9. pressure-responswe device, silid speed di ering from -the sive device connected to said fluid pressure normal rotational speed of said bbdyi generating means, 'means operated by the Intatimony whereof, I have hereunto ressure-responsive mechanism fol" indicatsubscribed my name this fifth day of Decemmg the rotational speed of the body, and a ber, 1924.

reed vibrated by the body at a predetel mined v F. SCHMIDT. 

